Hydrazine hydrate (1:1) → 6-Fluoro-3-(2-fluorobenzyl)-1H-pyrazolo[4,3-b]pyridine

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Reaction Steps

9.07 g (32.4 mmol) of the compound from Example 14A were initially charged in pyridine (84 ml). Subsequently, 8.10 g (162 mmol) of hydrazine hydrate and 19.8 mg (0.162 mmol) of 4-dimethylaminopyridine were added, and the mixture was heated to reflux for 30 min. The reaction mixture was diluted with ethyl acetate at RT and washed four times with 10% aqueous citric acid solution. The organic phase was subsequently washed with saturated aqueous sodium chloride solution, dried over sodium sulphate, filtered and concentrated. The residue was admixed with MTBE and the solids were filtered off. The latter were dried under high vacuum and gave 1.79 g (79%, 18% of theory) of the title compound. The filtrate was concentrated and gave a further 4.86 g (61%, 37% of theory) of the title compound. The two fractions were combined and converted without further purification.

Provenance & Evidence